Multiple choice

A boat travels from B to A upstream and from A to B downstream in 3 hours. If the speed of the boat in still water is 9 km/hr. and speed of the current is 3 km/hr., then the distance between the places A and B( in km.) is एक नाव स्थान B से स्थान A तक ऊर्ध्वप्रवाह तथा स्थान A से स्थान B अनुकूल 3 घंटे में चलती है | यदि स्थिर जल में नाव की चाल 9 किमी./घंटा है और धारा की चाल 3 किमी./घंटा है, तो स्थान A और स्थान B की दूरी ( किमी. में ) है |

  1. 10

  2. 12

  3. 14

  4. 16
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B Correct answer
Explanation

Upstream speed = 9 - 3 = 6 km/hr. Downstream speed = 9 + 3 = 12 km/hr. Total time = 3 hours for both trips. If d is distance: d/6 + d/12 = 3. Solving: 2d/12 + d/12 = 3, so 3d/12 = 3, giving d = 12 km. The faster downstream speed covers more distance in the same time.

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